In the past various refractory fiber products have been developed for use in high temperature applications. My U.S. Pat. Nos. 4,396,792 and 4,358,630, the subject matter of which is incorporated herein by reference are examples of the use of refractory fiber as a protective coating and structural member for small molten metal temperature measuring devices. Although these refractory fiber devices have provided good results; their useful life or test repeatability is limited. Also, the cost of refractory fiber is high thus limiting its usefulness for large items.